Print shifted

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mhandley
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Joined: Wed May 07, 2014 4:51 am

Print shifted

Post by mhandley » Fri Aug 19, 2016 2:28 pm

About 1/8" into this print everything shifted to 1 side by about 1/16
I have the machine running on a UPS so power glitch is not the issue.
The ABS part was VERY well adhered to the blue tape

Any Thoughts or suggestions besides just trying again?
This was a first prototype so I will be modifying and reprinting but I don't know how to fix this
STL and photos attached

Thanks in advance
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Jules
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Re: Print shifted

Post by Jules » Fri Aug 19, 2016 3:30 pm

Never printed ABS, and I'm not sure about issues with your version of the machine, so any suggestions I could give would be pretty generic. (Take them with a grain of salt.) ;)

Usually the problem of shifting prints is caused by the nozzle hitting part of the print and getting knocked out of whack. If you had the print stuck down really securely, that might be what happened. (Does ABS warp up when it prints?)

If the problem persists though, I would check the teeth on the pinion gear to make sure that they are not getting worn down and skipping steps. Your machine is a couple years old based on your join date....it might need to be replaced if it has had heavy use.

Edit: Just saw that Ed has a good discussion on the pinion gear with pictures in this thread:

viewtopic.php?f=7&t=1930#p8819

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insta
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Re: Print shifted

Post by insta » Fri Aug 19, 2016 4:31 pm

One edge warped off the tape, your nozzle struck it, you skipped steps.
Custom 3D printing for you or your business -- quote [at] pingring.org

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ednisley
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Re: Print shifted

Post by ednisley » Fri Aug 19, 2016 4:38 pm

mhandley wrote:everything shifted to 1 side by about 1/16
Judging from the top picture, the skip occurred either at or just above the bridging layer.

The recess produces two very very acute angles at the rim which provide essentially no anchors for the bridge. With poor anchoring, the bridging filaments bunch up and whack the nozzle as it passes overhead. One good whack stalls the stepper motor and produces exactly what you see.

If you have the option, redesign the recess to square off those points, perhaps by extending the edges straight back from the holes to the rim. Not as stylin', perhaps, but more suited to the process.

The snag need not come from those angles, though. The holes look raggedy enough to have the same problem, particularly the holes in the bridged area: it's difficult to build a hole in a shelf unless you have really good support underneath.

I build support directly into the model, rather than depend on auto-generated support, and you might get better results that way. A fancy asterisk provides good support for holes in bridges:
https://softsolder.com/2016/02/10/vacuu ... e-sockets/

Image

Those punched out easily and left a clean recess:

Image

mhandley
Posts: 8
Joined: Wed May 07, 2014 4:51 am

Re: Print shifted

Post by mhandley » Fri Aug 19, 2016 9:48 pm

Thanks fellas.
It was really stuck down and believe me I know what lifted parts look like ;)
I pretty much stopped printing for quite a while out of lift frustration.
I'm gonna go with the ed solution on this but I'll definitely be watching for the lifting part as well.
And now that I know what the mechanism is for the error I'll be able to keep an eye out and plan a little better.

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ednisley
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Re: Print shifted

Post by ednisley » Sat Aug 20, 2016 12:17 am

mhandley wrote:It was really stuck down
When the nozzle whacks a lump of plastic, you get Hobson's Choice:
  • Poor adhesion releases the whole thing to produce a floating bird's nest
  • Good adhesion holds the part & nozzle in place while the steppers scream in frustration
The combination of good adhesion and no layer bunching can be, mmmm, elusive:
https://softsolder.com/2015/10/11/sony- ... pod-mount/

Image

Yet another Thingiverse model with design features ill-suited to 3D printing...

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